Dietary habits of a large, long-lived endangered Australian percichthyid, the eastern freshwater cod, Maccullochella ikei.
Butler, G.L. and Wooden, I.J., 2012. Dietary habits of a large, long-lived endangered Australian percichthyid, the eastern freshwater cod, Maccullochella ikei. Endangered Species Research, 16: 199–209.
[available online: doi: 10.3354/esr00406]
SummaryThe eastern freshwater cod (Maccullochella ikei Rowland 1985) is an endangered fish species native to the Clarence and Richmond River catchments of northern New South Wales, Australia. Its diet was studied over two consecutive years in the Mann and Nymboida rivers to determine its summer and winter feeding habits. Food items were extracted using a non-lethal stomach flushing technique. A total of 268 cod (ranging in size up to nearly 1m long and 14 kg in weight) were caught, sampled and then released over the two years of the study. 191 fish contained at least one food item. There was a large variety and size range of items recovered, ranging from small aquatic insects to relatively large terrestrial animals such as rats, mice and a bandicoot. There were also significant differences between the food items consumed by cod in summer and winter. Cod ate more crustaceans, small fish and terrestrial animals in winter, and more aquatic insects and molluscs in summer. There were large differences in the food items consumed among different sized fish, with larger cod eating fewer crustaceans and more large fish and terrestrial animals. This study has shown that the eastern freshwater cod has a varied diet, and changes what it eats and how it feeds as it grows.
Prior to European settlement, eastern freshwater cod was distributed from the large slow-flowing lowland sections through to the highland streams throughout the 2 river systems. However, a major decline in abundance and distribution occurred in both populations throughout the 20th century. By the 1970s only one self-sustaining cod population remained – the one sampled in the Mann/Nymboida system. This new information about its diet will help in developing techniques to re-establish the species in other parts of its former range.